1. Field of the Invention
The present invention is broadly concerned with anti-tamper assemblies for use in preventing removal of bodies mounted on surfaces through use of a fastener. More particularly, the invention is concerned with such anti-tamper assemblies which may be used in conjunction with proximity or movement-sensing switches and include an access-blocking element such as a plug or magnetic component (e.g., a magnet) located in an anti-tamper position relative to the fastener, together with an anti-tamper switch which is operably coupled with the access-blocking element for actuation of the anti-tamper switch upon movement of the access-blocking element from the anti-tamper position thereof.
2. Description of the Prior Art
Security alarm systems often make use of magnetically actuatable switches attached to doors and windows for detecting unauthorized openings. One type of switch utilized in this context is a reed switch. However, reed switches are subject to unauthorized manipulation through use of an external magnet. Specifically, a compact high-energy magnet may be positioned in proximity to the reed switch, which will then be operated to either open or close the switch depending upon the control scheme. Once this is accomplished, an intruder may open the door or window without triggering the alarm system.
In response to these problems, the Magnasphere Corporation of Waukesha, Wis. has introduced improved switches not subject to external magnetic manipulation. These switches typically include a pair of spaced-apart switch elements with a shiftable body (e.g., a spherical ball) moveable between respective positions corresponding to different switch conditions. Thus, the ball may be in simultaneous contact with the switch elements in one condition, and out of such simultaneous contact in another condition. An alarm circuit is electrically coupled to the switch elements in order to generate an alarm signal upon a change in switch condition. The Magnasphere switches are described in U.S. Pat. Nos. 5,332,992; 5,530,428; 5,673,021; 5,889,659; 5,977,873; 6,087,936; 6,506,987; 6,603,378; 6,803,845; 7,023,308; 7,248,136; and 7,291,794. Other magnetic switches are described in U.S. Pat. Nos. 5,668,533 and 5,877,664.
In many instances it is necessary to mount alarm system components on the surfaces of doors or windows to be protected using fasteners such as screws, rather than having these components embedded within the protected structures. Such surface-mounted alarm systems can be vulnerable because the one or more of the switch components may be detached by the simple expedient of removing the fasteners. Accordingly, in order to protect the integrity of surface-mounted alarm systems or more broadly any surface-mounted body, an anti-tamper alarm assembly is required.